PHENOTYPIC EVALUATION OF GROUP-1 Β-LACTAMASE IN THE INDIGENOUS GRAM-NEGATIVE PATHOGENS: IMPLICATIONS FOR ANTIBIOTIC RESISTANCE MANAGEMENT

Abstract

The extensive use of β-lactam antibiotics has led to widespread bacterial resistance, primarily due to β-lactamase enzymes that hydrolyze the β-lactam ring in antibiotics such as penicillin, cephalosporins, carbapenems, and monobactams. These enzymes are classified by the Ambler molecular and Bush-Jacoby functional schemes, with Group 1 β-lactamases capable of hydrolyzing broad-spectrum antibiotics and often resisting the inhibitors such as clavulanic acid and tazobactam. This study aimed to identify β-lactamase and Group 1 β-lactamase production among clinical Gram-negative bacteria. From June 2020 to June 2021, about 235 GNB isolates were collected from various clinical specimens at Diagnostic Laboratories, Hyderabad. After subculturing and confirmatory testing, 220 isolates were included. Of these, 50.5% were from male and 49.5% from female patients, with urine (48.1%) being the most common specimen source. β-lactamase production was detected in 74% (n=163) of isolates using the iodometric strip method. All S. typhi isolates were positive, followed by Acinetobacter (85.7%), E. coli (77.8%), P. aeruginosa (70.2%), K. pneumoniae (68.1%) and P. mirabilis (64.2%). Among β-lactamase producers 33.1% (n=54) strains were identified to produce Group 1 beta-lactamase. Categorically all the Acinetobacter strains produced these enzymes, while none of the S. typhi did. K. pneumoniae showed the highest prevalence (i.e. 36.6%) among remaining species, followed by P. mirabilis (33.3%), E. coli (30.8%), and P. aeruginosa (27.2%). These findings underline the prevalence of β-lactamase-mediated resistance and the significance of Group 1 enzymes in clinical Gram-negative bacterial isolates.